bis( diphenylphosphino)

Nov 21, 1979 - protonated dppe ligand ( [ P ~ ~ P C H ~ C H P P ~ Z ] ) and a cationic vinylidene moiety. Subsequent intramolecular cyclization pro- d...
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7232

Journal o f t h e American Chemical Society

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101:24

1 November 21, 1979

Cationic Vinylidene Complexes. Preparation and Structural Characterization of ( q5-Cyclopentadienyl)(2-methyl-4,5bis( diphenylphosphino)-2-penten-3-yl)iron(11). A Base- Induced Interligand Reaction in a Vinylidene Complex Richard D. Adams,* Alan Davison,* and John P. Selegue Contribution f r o m the Departments of Chemistry, Yale University, New Haven, Connecticut 06520, and Massachusetts Institute of Technology, Cambridge, Massachusetts 021 39. Received May 21, 1979

Abstract: The cationic vinylidene complex [(Cp)Fe(dppe)[C=C(CH3)21] [SOjF] (la) (dppe = 1,2-bis(diphenylphosphino)ethane), prepared by the methylation of (Cp)Fe(dppe)(C=CCHJ) (11), is smoothly deprotonated by potassium hydroxide or sodium bis(trimethylsilyl)amide. The exclusive product is (Cp) Fe[Ph2PCH*CH(PPh2)d=C(CH3)2]( I 1 I), which contains a novel ferradiphospha[2.1,l]bicyclohexanering system, This prgduct was investig:ted by spectroscopic and crystal structure analysis: space group Cc, a = 14.738 (4) A, b = 12.471 (5) A, c = 16.982 (7) A, fl = 106.17 (3)O, V = 2997 (4) A3, Z = 4, &&d = 1.268 g/cm3. Refinement on 1668 reflections with FOZ> 3 0 ( F O 2 )has yielded the final discrepancy indices R = 0.058 and R, = 0.060. The bicyclic ring system shows geometric and spectroscopic features which indicate that significant torsional strain is present. The formation of 111 has been explained by the intermediacy of a zwitterionic complex containing both a deprotonated dppe ligand ( [ P ~ ~ P C H ~ C H P Pand ~ Za ]cationic ) vinylidene moiety. Subsequent intramolecular cyclization produces I I I .

Introduction Little is known of t h e reaction chemistry of vinylidene complexes of transition metals (L,,M=c=cR~).~-' Cationic vinylidene complexes have been observed to undergo addition of alcohols and water to product alkoxycarbene or acyl complexes,'.? displacement of and nucleophilic addition to the vinylidene ligand by hydride and reversible deprotonation of monosubstituted vinylidene ligands a t P-carbon atoms. I A L ~Neutral vinylidene complexes have been observed t o undergo thermal elimination of the vinylidene ligand,5 interconversion of terminal and bridging vinylidene ligands: and ir coordination by a n Fe(CO), moiety.7 W e have shown that electron-rich alkynyl complexes of iron readily react with electrophiles to produce stable cationic vinylidene complexes (Ia-d).3 This reaction provides a convec

Ia, L + L b, L + L c , L + L' d, L = L

dppe;* R = R' = CH, dppe; R = CH,; R = H = dppe; R = R'= H = P(CH,),; R = R' = CH, = =

nient method for the preparation of such complexes, so t h a t their chemistry can be systematically explored. I n this paper, we report the synthesis and characterization of t h e product obtained by t h e deprotonation of vinylidene complex la.

Experimental Section General Procedures and Starting Materials. All operations involving the handling of organometallic complexes in solution were carried out under > i n atmosphere of prepurified nitrogen or argon. Air-sensitive iiiaterialh wcrc handled using standard inert atmosphere techniques, or in ;I Vacuum Atmospheres drybox. Ethers and hydrocarbon solvents were distilled from sodium benzophenone ketyl before use. Other aolvcnta were degassed with a dispersed stream of dry nitrogen and stored over molecular sieves. Methyl fluorosulfonate (Aldrich) was 0002-7863/79/1501-7232$01.00/0

distilled under nitrogen and stored at - 15 "C. FeCIz(thf)~,~ cyclopentadienylthallium ( I),Io and sodium bis(trimethylsilyl)amide' I. were prepared by literature methods. (Cp)Fe(dppe)CI was prepared by a modification of the method of Mays and Sears.12Other reagents were used as received from commercial sources. ' H N M R spectra were obtained on a Hitachi Perkin-Elmer R20B spectrometer (6b MHz) or a Bruker HFX270 spectrometer (270 MHz) and are reported in parts per million downfield from internal Me4Si (6). I3C N M R spectra were obtained on a JEOL FX60Q spectrometer ( 1 5 MHz, FT mode) and are reported in parts per million downfield from internal Me& (6~).3 1 PN M R spectra were obtained on a Varian CFT 20 spectrometer (32.2 MHz, FT mode) and are reported in parts per million downfield from external aqueous H3P04. Mass spectra were obtained a t 70 eV on a Varian Associates MAT 44 (low resolution) or a Consolidated Electrodynamics Corp. 21-1 I O (high resolution). Infrared spcctra were recorded on Perkin-Elmer Model 457A and 180 spectrophotometers. UV/visible spectra were obtained on a Cary Model I7 spectrophotometer. Melting points were determined on samples i n scalcd evacuated capillaries using a Mel-Temp apparatus and are uncorrected. Elemental analyses were performed by Galbraith Laboratories Inc., Knoxville, Tenn. Preparation of (Cp)Fe(dppeHC=CCH3). Propynyllithium (Alfa, 0.69 g, 15.0 mmol) and (Cp)Fe(dppe)CI (5.0 g, 90.4 mmol) in 100 mL of T H F were stirred for 7 h at room temperature. The solvent was rcnioved in vacuo at 40-50 "C. The dark brown residue was extracted batchwise with benzene (ca. 50 mL) until the extracts were colorless, I'iltcrcd. and reduced in volume. The red-brown solution was chromatographed on silica gel. Benzene eluted dark-colored impurities, and the product was eluted with ethyl ether. Recrystallization from warm benzene/heptane gave pure red-orange crystals ( I .57 g, 32.370, ill17 178.5-180.5 "C). Anal. Calcd for C34H32FeP~:C, 73.13; H. 5.78; P, I I .09. Found: C . 73.02; H, 5.96; P. 10.90. Mass spectrum: parent ion m/e 558. I R : v(C-C) 2100 cm-'. ' H N M R (60 MHz, CDC13): 6 8.0-7.2 (20 H. Ph), 4.17 (t, 3 J p =~ 1.3 Hz, 5 H, Cp). 2.9-1.9 (m, 4 H, PCHl), 1.60 (t, 'Jp!, = 2.15 Hz, 3 H, CH3). "C NMRI3 (15 MHz, CDCI,): 142.7-127.1 (m, Ph), 112.6 (s,C,),97.5 (s,C$).78.8 (s, Cp),28.4 (t. IJpc = 22.5 Hz, PCH2), 7.7 ppm (s, CH3). UV/vis (CH3CN): 475 nm, 6 450 (shoulder on intense U V absorption). Preparation of [(CpiFe(dppe){C=C(CH3)2)1S03F. One gram ( 1.79 miiiol) of (Cp)Fe(dppe)(C=CCHj) was dissolved in 25 mL of ben/cnc. and 0.1 7 mL (0.24 g, 2.1 mmol) of methyl fluorosulfonate was added to the stirred solution during about 5 min. A pale orange solid prccipitntcd on addition. and 15 m L of benzene was added to improve 4tirring. After 30 imin the solids were filtered out. washed with benicnc. cthcr, and petroleum ether. and dried in vacuo. The yield was

0 1979 American Chemical Society

Adams, Dauison, Selegue

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7233

quantitative ( I .2 g). Recrystallization from CHC13 or CH*Clz/benTable I. Experimental Data for the X-ray Diffraction Study of (v5-C5H~)Fe[PPh2CH2CH(PPh2)C=C(CH3)2] 7cnc gave lustrous orange plates (nip 230.5-232.5 OC dec). Anal. Calcd for C3sH35FFe03PlS: C, 62.51; H, 5.25; P, 9.21; S, A. Crystal Parameters at 23 "C 4.77. Found: C , 62.41; H, 5.30; P. 9.20; S, 4.45. IR: v(C=C) 1675, space group cc v(S03F-) 1280, 1090, 1065 cm-I. IH N M R (60 MHz. I : I U 14.738 (4) A CDC13/CD2C12): 6 7.7-6.9 (m, 20 H , Ph), 5.06 (t, 3 J p = ~ 0.8 Hz, 5 b 12.471 ( 5 ) A H. Cp). 2.86 (d, 'JPH = 13.0 Hz, 4 H, PCH*), 0.96 (t, 'JPH= 0.8 Hz, C 16.982 (7) A 6 H, CH3). I3cN M R ( l : l CDC13/CD2C12): 363.3 (t, ' J p c = 33.3 106.17 (3)" P HI, C,,), 136.5-129.6 (m, Ph), 127.8 (s,C,j), 88.0 (s, Cp), 28.4 (t, l J p c V 2997 (4) A3 = 23 0 H7, PCH2), 12.0 ppm (s, CH3). Z 4 Preparation of (C~)~~[P~~PCH~CH(PP~~)C=C(CHJ)~] (111). A. 572.14 mol wt [ (Cp)Fe(dppe){C=C(CH3)5\][S03F] ( I .ig, 1.8 mmol) was prepared 1.268 g cm-3 Pcalcd from (Cp)Fe(dppe)(C=CCHj) (1.0 g) and CHjSO3F (0.17 mL) in benzene (50 mL). All volatiles were removed in vacuo and the pale B. Measurement of Intensity Data o r a n g solid was suspended in 30 mL of ethyl ether. Sodium bis(triradiation Mo Ka (0.710 ?3 A) nicthylsily1)amide (0.35 g, 1.9 mmol), was added over a period of graphite monochromator about 1 min with vigorous stirring. After 5 min, the deep red solution detector aperture was filtered and 5 mL of hexanes was added. The volume of the sohorizontal: A t B tan 8 A = 2.6 mm lution was reduced to I O mL in vacuo, and it was cooled to -1 5°C B = 1.2 mm overnight. Filtration, washing with petroleum ether, and drying in vertical: 4 mm vacuo,gave pure red crystals (0.67 g, 65.6%, mp 190-191 "C dec). reflections measured t h , + k , tl Anal. Calcd for C35H34FeP~:C, 73.43; H, 5.99; P, 10.82. Found: 470 max 28 C. 73.49; H, 6.10; P, 10.86. Mass spectrum: parent ion m/e 572.1442 scan type moving crystal/stationary counter (calcd. 572.141 I ) ; parent - PPhz m/e 387.0942 (calcd, 387.0965). 0.8" 0.347 tan 19 scan width IR (mulls): 1433 (s), IO94 (s, br), 850 (s), 799 (s), 751 (s), 742 (s), background '14 additional scan at each end of scan 715 (a), 697 (vs), 533 (s), 527 (s), 491 (s) cm-I. ' H NMR (270 MHz, scan rate max 10°/min C6Dh): 6 7.82, 7.56,7.39 (each hasJpH 3 ~ . O , J H - H= 7.2 Hz, 2 H, 1.3"/min min Ph,,th,), 7.2-6.9 (m, 14 H, Ph), 4.47 ( J P - H ~= 44.8, JP'-Ha = 7.3, no. reflections measured 1880 3 J H a - H b = 4.2, 3 J ~ a3- 0~HZ, c I H, PC/faCHbHcP), 4.41 ( 3 J p = ~ data used ( F 2 > 3.0 u ( F 2 ) )1668 1.5, 3 J p ' H = 0.7 HZ, 5 H, c p ) , 2.29 (JP-Hb = 43.3, JP'LHb = 10.1, 'JH~.H =~ 4.2, 'JHb.Hc = 13.0 HZ, 1 H, PCHaCHbHcP), 2.05 (JPH = 2.2, JP'LH = 2.1 Hz,3 H , CH3), 1.98 (JPH = 3.2, Jp" = 3.0 Hz, 3 H, CH3), I .87 ( J P - H =~ 16.9, J p ' c ~= ~4.6, 3 . / ~ a - ~ c 0 , = 13.0 Hz, 1 H, PCHaCHbHcP). I3C['H] N M R ( 1 5 MHz, C6D6): All calculations were performed on a Digital PDP 1 1 /45 computer 147.9-126.3 (m, Ph vinylic carbons), 74.4 (s, Cp), 56.9 (dd, Jpc using the Enraf-Nonius SDP program library. Anomalous dispersion = 37.4, Jp-c = 16.8 Hz, CH), 33.3 (d, J p c = 35.2 Hz, CHl), 26.3 corrections14a were included for the of all nonhydrogen (d, JPC= 2.9 Hz, CH3), 20.9 ppm (poor t, JPC= Jp'c = 4.4 Hz, CH3). atoms. Least-squares refinements minimized the function z.hk/W(Fo 3 ' P [ ' H ] N M R (32.2 MHz, C6Hh): 86.63.42.29 ppm (AB, ) J p - p = - Fc)2 where the weighting factor w = l / ~ r ( F ) ~ . 44.8 Hz). Solution and Refinement of the Structure. The positions of the iron B. I n a septum-capped vial were placed [(Cp)Fe(dppe)and phosphorus atoms were determined from a Patterson map, and {C=C(CH3)2)] [S03F] (ca. 50 mg) and potassium hydroxide (ca. 200 the positions of carbon atoms were obtained by successive difference mg). T H F (5 mL) and a few drops of water were added by syringe, Fourier techniques. Hydrogen atom positions were calculated and and the slurry was shaken for 3 h at room temperature. The resulting were included in structure factor calculations but they were not reorange-red solution was decanted from the oily aqueous layer, dried fined. Full-matrix least-squares refinement using anisotropic thermal over CaC12, and reduced to dryness. The residual red oil was dissolved parameters for the iron and phosphorus atoms and isotropic thermal in 2 mL of ether and cooled to - 15 OC overnight. The deep red crystals parameters for the carbon atoms converged to the final residuals R1 which formed were washed with pentane and dried in vacuo. Infrared = 0.058 and R2 = 0.060. and mass spectra identified the product as 111. To test for the proper enantiomorph the signs of the coordinates of Crystal Preparation and Data Collection for all atoms were reversed and three additional cycles of refinement were (CP)Fe[PPh2CH2CH(PPh2)C=C(CH3)2] (111). Single crystals were performed. The residuals were then R1 = 0.058 and R2 = 0.061. Algrown by recrystallization from ethyl ether at -20 OC. A thick, though this difference is not significant, the final atomic coordinates crystalline plate of approximate dimensions 0.09 X 0.20 X 0.35 mm and thermal parameters presented in Table I1 are based on the original was selected and mounted in a thin-walled-glasscapillary.The crystal model, since the value of R2 for that model was slightly lower. The faces were subsequently identified as 1 I O , 1 IO, 1 IO, ITO, 001. and 001. largest peaks in the final difference Fourier synthesis were 0.217 and The crystal was mounted with the c * direction 13' from the diffrac0.206 e/A3. tometer axis. The largest value of the shift/error parameter on the final cycle of All diffraction measurements were performed using an Enrafrefinement was 0.05. The error in an observation of unit weight was Nonius CAD-4 fully automated four-circle diffractometer using 2.89. Bond distances and angles with errors from the inverse matrix graphite monochromatized Mo KO radiation. The unit cell was deobtained on the final cycle of least-squares refinement are listed in termined from 25 randomly chosen reflections using the CAD-4 Tables 111 and IV. Tables of structure factors and intermolecular search, center, index, and least-squares routines. Crystal data are listed contacts are available (see supplementary material). in Table I . From a total of I880 reflections, 1668 conformed to the relation Results F 2 2 3u(F2) and were used in the structure solution and refinement. Preparation of the Complex. The synthetic scheme shown The value of thep factor used in calculating u(F2)was 0.02. Standard below was used to prepare complex 111. T h e reaction of reflections monitored periodically showed less tban 2% change in intensity during data collection. The linear absorption coefficient was (Cp)Fe(dppe)C1I2 with L i C G C C H 3 in T H F gives ( C p ) 6.459 cm-I, and no absorption correction was applied. Fe(dppe)(C=CCH3) (11) in 32% isolated yield. This product The pattern of systematic absences observed during data collection, reacts rapidly and quantitatively with methyl fluorosulfonate hkl, h k = 2n + I , and h01, I = 2n t 1, is consistent with either of in benzene to produce the isobutenylidene complex la. Dethe space groups C2/c or Cc. The calculated density was 1.268 g/cm3, protonation of la was accomplished with either aqueous poindicating the presence of four molecules in the unit cell. tinder these tassium hydroxide in T H F or sodium bis(trimethylsily1)amide conditions the molecule would be required t o contain a center of in ethyl ether. The latter reaction allows a simpler workup and symmetry in space group C2/c. We considered this unlikely and thus yields analytically pure I I I in 66% yield. N o products arising chose the space group Cc to begin our calculations. The successful from nucleophilic attack at the vinylidene N carbon3b could solution and refinement of the structure proved this choice to be correct. be detected using either base."

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1 101:24 1 November 21, 1979

Table 11. Final Positional and Thermal Parameters and Their Estimated Standard Deviations for

(Cp)f’e[P P ~ ~ C H ~ C H ( P P ~ Z ) C = C (aC H ~ ) ~ ] atom

v

x 0.000 0.0749 (2) -0.1207 (2) 0.1014 (7) 0.0978 (8) 0.1 145 ( I O ) 0.1351 (9) 0.1431 ( I O ) 0.1225 (9) 0.1824 (7) 0.2688 (8) 0.3519 (8) 0.3524 (9) 0.2692 ( 1 1 ) 0.1827 ( I O ) -0. I379 (7) -0.1679 (8) -0.1756 (8) -0.1580 (9)

0.0262 ( 1 ) -0.0303 (2) -0.0596 (2) -0.1681 (9) -0.201 7 (9) -0.3095 ( 1 1) -0.3802 ( 1 I ) -0.3522 (12) -0.2418 ( I O ) 0.0408 (8) -0.0005 (9) 0.0531 ( I O ) 0.1480 ( I O ) 0.1930 (13) 0.1381 (13) -0.2004 (8) -0.2235 (9) -0.3297 ( I O ) -0.4123(ll)

atom

R

7

0.0000 0.1211 (2) 0.0148 (2) 0.1538 (6) 0.2308 (7) 0.2524 (9) 0.2024 (9) 0.1274 (9) 0.1024 (8) 0.1765 (6) 0.1789 (7) 0.2162 (8) 0.2532 (8) 0.2474 ( I O ) 0.2157 (9) -0.0171 (6) -0.1001 (7) -0.1268 (7) -0.0748 (8)

I’

X

-0. I292 (9) -0.1 186 (8) -0.2394 (6) -0.2495 (8) -0.341 8 ( 1 0) -0.4173 (9) -0.4098 (8) -0.3208 (8) -0.1062 (7) -0.0241 (7) -0.0354 ( 7 ) -0.0608 (9) -0.0771 ( I O ) -0.0705 ( 1 2) 0.0332 (9) -0.0364 (8) -0.0054 (9) 0.0910 (9) 0.1 110 (8)

3.2 (2) 4.3 (3) 6.3 (3) 6.4 (3) 6.5 (3) 5.1 (3) 3.4 (2) 4.3 (3) 5.4 (3) 5.6 (3) 8.5 ( 5 ) 7.3 (4) 3.2 (2) 3.9 (2) 4.8 (3) 5.4 (3)

-0.3919 (IO) -0.2853 ( I O ) -0.0059 (8) 0.0933 ( I O ) 0.1377 ( 1 2 ) 0.0793 ( I 1) -0.0146 ( I O ) -0.0624 (9) -0.0538 (8) 0.0210 (9) 0.1 142 (9) 0.2133 ( 1 1 ) 0.2455 (12) 0.2998 ( 1 5 ) -0.0423 ( I O ) 0.0346 ( 1 1) 0.1326 ( I I ) O.l185(lI) 0.0117 ( I O )

-0.0059 (8) 0.0370 (7) -0.0327 (6) -0.0674 (7) -0.1049 (9) -0,1008 (8) -0.0677 (7) -0.0323 (7) 0.1281 (6) 0.1582 (6) 0.0875 (6) 0.1063 (7) 0.1861 (9) 0.0469 ( 1 I ) -0.1021 (8) -0.1276 (8) -0.0988 (8) -0.0497 (8) -0.0551 (8)

Anisotropic Thermal Parameters for the Iron and Phosphorus Atoms P(2A P(3,3) PC 1.2) P( 127) Fe 0.003 86 (6) P(l)0.0038 ( I ) P(2) 0.0035 ( I )

0.005 72 (9) 0.0045 (2) 0.0052 (2)

0.002 46 (4) 0.002 45 (9) 0.002 68 ( I 0)

The form of the anisotropic thermal parameter is exp[-(P(l,l)h*

0.0005 (2) 0.0010 (3) 0.005 (3)

t P(2,2)k2

B

Z

5.6 (3) 4.5 (3) 3.0 (2) 5.1 (3) 6.7 (4) 5.7 (3) 5.0 (3) 4.1 (2) 3.3 (2) 3.1 (2) 3.6 (2) 5.4 (3) 6.3 (3) 9.5 ( 5 ) 5.4 (3) 5.6 (3) 6.3 (3) 5.8 (3) 5.4 (3)

P(2,3)

0.002 17 (8) 0.0014 (2) 0.0018 (2)

0.0012 (2) -0.001 1 (3) 0.0003 (3)

+ P(3,3)/2 t P(1,Z)hk t P(1,3)hl+ /3(2,3)k/)].

Table 111. Bond Distances with Errors for (Cp) Fe[ PPh2CH 2CH( PPh*)C=C( C H 3)2] atoms

CPI

Fc- P( I )

Fc-P(2) I.‘c C ( h l ) l.’c CP( I ) I ’ c CP(2) ~ Fc CP(3) t ‘c C P( 4) 1.c CP(5) l’(l)-C(ll) I’( I)-C(21) P( I )-C(52)

2

~

Figure 1. An ORTEP diagram of (Cp)ke[PPhzCHzCH(PPhl)C= C ( C H j ) ? ]\howin&50% probability ellipsoids The phenyl groups have

bccn eliminated for clarity

I’(2)-C(31) P(2)-C(.ll) P(2)-C(51) CP(I)-CP(2) CP(2)-CP(3) CP(3)-CP(4) CI’(.l)-CP(5) CI’(S)-CP(I)

CpFe(dppe)CI

II

+ LiCECCH3

+ CH3OS02F

-

-

( C p ) F e ( d p p e ) ( C = C C H 3 ) (11)

(1)

C ( l I)-C(12) C(12)-C(13) C( l3)-C( 14)

C(14)-C(15) C(I5)-C(lh)

[(Cp)Fe(dppe)lC=C(CH3)211 [ S 0 3 F l (la) la base 111

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distance, A 2.164(2) 2. I50 (2) 2.030 (7) 2.1 10 (8) 2.084 (9) 2 . I23 (9) 2.1 14 (8) 2.107 (8) 1.815(7) 1.830 ( 7 ) 1.856 (7) 1.834 (7) 1.837 (6) 1.877 (7) 1.383 ( 1 1 ) 1.349 ( I I ) 1.444 (12) 1.373 ( I O ) 1.377 ( I O ) 1.388 (9) 1.397 ( I O ) 1.316 ( 1 I ) 1.357 ( 1 1 ) 1.448 ( I I )

atoms

C(16)-C(ll) C(21)-C(22) C(22)-C(23) C(23)-C(24) C(24)-C(25) C(25)-C(26) C(26)-C(21) C(31)-C(32) C(32)-C(33) C(33)-C(34) C(34)-C(35) C(35)-C(36) C(36)-C(31) C(41)-C(42) C(42)-C(43) C(43)-C(44) C(44)-C(45) C(45)-C(46)

C(46)-C(41) C(51)-C(52) C(52)-C(61) C(61 )-C(62) C(62)-C(63) C(62)bC(64)

distance, 8, 1.363(9) 1.364 (9) 1.385 (9) 1.339 ( I O ) 1.327 ( I I ) 1.415 (13) 1.384 ( I I ) 1.385 (9) 1.394 ( I O ) 1.335 ( I O ) 1.340 ( I O ) 1.424 ( I O ) 1.378 (9) 1.360 (9) 1.441 ( 1 1 ) 1.348 ( I I )

1.290(10) 1.414 (10) 1.392 (9) 1.500 (9) 1.646 (9)

I ,355 ( 10) 1.496(11) 1.455 (13)

(2) (3)

Description of the Structure. T h e molecular structure of compound I I I is shown in Figures 1 and 2. Figure 1 emphasizes the central coordination sphere of the iron atom, which contains a symmetrically bonded pentahaptocyclopentadienyl ring, a vinylic carbon, a n d two phosphorus atoms. T h e most important feature of the structure is that the vinylic CY carbon ( C ( 6 1 ) ) is bonded to both the iron atom and to one of the carbons in the ethylene bridge o f the dppe ligand ( C ( 5 2 ) ) . As a result, complex I l l contains a 1 -ferra-2,5-diphospha[2.1, I]bicyclohexane ring system. T h e torsional strain in the

bicyclic ring system is reflected in its geometry. T h e fourmembered ring has angles of 69.3 (2), 88.2 (2), 85.8 (4), and 99.0 (4)’ a t Fe, P(1), C(52), and C(61), respectively. This ring is “folded” with a dihedral angle o f 47.4’ between the FeP ( l ) - C ( 5 2 ) and the F e - C ( 6 1 ) - C ( 5 2 ) planes. T h e C ( 6 1 ) C ( 5 2 ) bond is abnormally long, 1.646 (9) A. T h e Fe-C(61) bond length is 0.10 A longer than the Fe-C (sp2) bond in ( C p ) F e ( d p p e ) C ( 0 ) P h i 6(2.030 (7) A). T h e five-membered rings show less sign of strain, although the P ( 2 ) - C ( 5 1 ) - C ( 5 2 ) angle is rather acute, 103.0 (4)’. T h e exocyclic double bond has a typical length for a carbon-carbon double bond, 1.36 (1)

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Table IV. Bond Angles with Errors for (Cp)te[PPh?CHzCH(PPh2)C=C(CH&] atoms

P( 1 )-Fe-P(2) P( I )-Fe-C(61) P(2)- Fe-C(6 1 ) Fe-P( I)-C(I'l) Fe-P( 1 )-C(21) Fc-P( 1)-C(52) C( I 1 )-P( I )-C(21) C(1 I)-P(I)-C(52) C(2I)-P(I)-C(52) Fe-P(2)-C(3 1 ) Fe-P(2)-C(4 1 ) Fe-P( 2)-C(5 1 ) C ( 3 I)-P(Z)-C(41) C ( 3 I )-P(2)-C(51) C(4 1 )-P( 2)-C(5 1 ) CP(5)-CP( 1 )-CP(2) CP( I )-CP( 2)-cP(3) CP( 2)-CP( 3)-CP(4) c P( 3)-cP(4)-CP( 5 ) CP(4)-CP(5)-CP(I) P(I)-C(l I)-C(I2) P( I )-C( I I )-C( 16) C ( I 6)-C( 1 I)-C( 12) C(I l ) - C ( l 2 ) - C ( l 3 ) C( l2)-C( 13)-C( 14) C( 13)-C( 14)-c( 15) C( 14)-C( 15)-C( 16) C ( I5)-C( I6)-C( 1 1 ) P( l)-C(2I)-C(22) P( 1 )-C(21 )-C(26) C(26)-C(2 I )-C(22)

angle, deg

atoms

angle, deg

86.96 (7) 69.3 (2) 78.1 (2) 127.5 ( 2 )

C(2 1 )-C(22)-C(23) C( 22) -C( 23)-c( 24) C(23)-C(24)-C(25) C(24)-C(25)-C(26) C(25)-C(26)-C(2 1 ) P( 2)-C( 3 1 ) -C( 32) P(2)-C(3 I)-C(36) C(36)-C(3 1 )-C(32) C(3 I)-C(32)-C(33) C(32)-C(33)-C(34) C( 33)-C( 34) -C( 35) C(34)-C(35)-C(36) C( 3 5)-C( 36)-C( 3 1 ) P(2)-C(41)-C(42) P(2)-C(41 )-C(46) C(46)-C(4 I )-C(42) C(4 I)-C(42)-C(43) C(42)-C(43)-C(44) C( 43)-C( 44)-C( 45 ) C(44)-C(45)-C(46) C(45)-C(46)-C(41) P(2)-C(5 I)-C(52) P( I)-C(52)-C(51) P( I)-C(52)-C(61) C(5 I)-C(52)-C(61) Fe-C(6 I )-C(52) Fe-C(61 )-C(62) C(52)-C(6 I )-C(62) C(6 1 )-C(62)-C(63) C(6 1 )-C( 62)-C( 64) C(63)-C(62)-C(64)

122.0 (7) 122.0 (8) 117.1 (9) 122.6 ( I O ) 119.3 (9) 118.6 (5) 123.5 ( 5 ) 117.8 (6) 120.2 (7) 122.3 (8) 118.6 (8) 121.8 (8) 1 19.2 (7) 1 19.9 ( 5 ) 122.0 (5) 1 18.2 (6) 121.1 (8) I 17.4 (9) 122.8 (9) 121.6 (8) 118.9 (7) 103.0 (4) 107.8 (5) 85.8 (4) 106.4 (5) 99.0 (4) 144.1 (6) 1 16.9 (6) 125.6 (8) 119.6 (8) 114.8 (8)

118.1 ( 2 )

88.2 (2) 102.7 (3) 110.2 (3) 108.0 (3) 119.5 (2) 119.0 (2) 103.8 (2) 100.6 (3) 107.9 (3) 105.0 (3) 105.5 (8) I 1 1.6 (8) 106.2 (8) 106.0 (8) 110.7 (8) 120.8 (5) 120.7 (6) 1 18.4 (7) 1 19.2 (7) 122.0 (9) 121.9 (9) 1 17.0 (9) 121.3 (8) I 20.0 (5) 123.9 (6) 116.1 (7)

A, and its substituents a r e nearly coplanar. T h e iron atom lies only 0.063 A from the plane containing atoms C ( 6 1 ) , C(62), C(63), C(64), and C(52). An Fe-C(61)-C(62) angle of 144.1 (6)" compensates for the very acute Fe-C(61)-C(52) angle. Other features of the coordination geometry of 111 a r e normal, and a r e in agreement with structural aspects of (Cp)Fe(dppe) c0mplexes.~6-~~ The unit cell for I11 consists of four well-separated molecules with no unusually short intermolecular contacts between nonhydrogen atoms. T h e closest approach is between C ( 13) and C ( 3 2 ) of adjacent molecules, 3.50 8, a p a r t . Spectroscopic Characteristics of Ill. Typically, the mass spectra of CpFe(dppe)X complexes display moderately weak molecular ions and fragment ions arising from the loss of dppe.3b,'2cT h e high-resolution mass spectrum of 111, on the other hand, displays a fairly strong molecular ion and a fragment ion corresponding to the loss of a PPhz unit, reflecting t h e fact t h a t the dppe ligand and the isobutenylidene moiety have become covalently linked. T h e 3 1 P [ ' H ]N M R spectrum of I11 consists of a n A B pattern for the two inequivalent phosphorus atoms, consistent with the lack of symmetry shown in its molecular structure. It is likely that P(2), which is contained in a five-membered chelate ring, is responsible for the downfield 3 1 P resonance (86.63 ppm), and that P ( I ) , which is contained in a four-memberei chelate ring, produces the higher field signal (42.29 p p m ) . ' 8 ' H NMR spectra (270 M H z ) of 111 show several interesting effects. T h e phenyl region exhibits remarkable fine structure, consisting of three well-separated apparent triplets each of relative intensity 2, a t 6 7.82, 7.56, and 7.39, in addition to a complex multiplet from 6 7 . 2 to 6.9. T h e apparent triplets all have J P - H = 8.0 Hz and collapse to doublets (with some fine = 7.2 Hz). structure) upon broad-band 3 ' P decoupling (JH-H These resonances may be due to the ortho protons of the three phenyl rings which a r e held in close proximity to the sterically locked bicyclic ring system (Figure 2). T h e cyclopentadienyl

C13

Figure 2. An ORTEP diagram of ( C p ) F e [ P P h 2 C H & H @ m = C(CH3)2] showing 50% probability ellipsoids.

group and the two methyl groups a r e all unequally coupled to the two phosphorus atoms. T h e remaining three protons (Ha on C(52), Hb and H, on C(51) of Figure 2) couple with the two phosphorus atoms to produce a very complex spin system (approximating A B M X Y ) . By a combination of 31Pand selective 'Hdecoupling, all proton shifts and coupling constants were determined (see Experimental Section). Of particular note is the strong downfield shift of H a on C(52), characteristic of a proton on the bridgehead carbon of a polycyclic system.19 T h e bridgehead carbon resonance ( C ( 5 2 ) ) also occurs a t low fieldi9 ( 6 56.9 ~ ppm) in the '3C[1H]N M R spectrum of 111,

Journal of the American Chemical Society

7236

Table V. Various Unit Weighted Least-Squares Planes for ( C P) t c [ PPhzC H 2C H ( PPhz)C=C(C H 3 ) 21 ‘

plane no.

atoms

I

c p i 1)

-0.003 -0.003 0.008 -0.01 0 0.008 - 1.748 -0.001 0.014 -0.003 -0.007 -0.003 -0.063 -1.102 1.764 0.003 -0.0 I2 0.005 0.012 -0.02 I 0.014 0.059 0.0 I0 0.0 I0 -0.00 I -0.03 1 0.052 -0.04 1 0.122 0.003 -0.009 0.0 I O -0.006 0.000 0.00 I 0.099 0.002 -0.01 2 0.01 5 -0.007 -0.004 0.007 -0.040

CP(3) CP(4) CP(5) Fe * C(61) C(62) C(63) C(64) C(52) Fe* P( 1 ) * Pi2)* C(11) C( 12) C(l3) C ( 14) ~(15) Ci16) Pi I )* Ci21) C(22) Ci23) ~(24) Ci25) Ci26) PI* C(31) ~(32) C(33) Ci34) Ci35) C(36) P(2)* Ci41) ~(42) Ci43) C(44) C(45) C(46) P(2)*

2

3

4

5

6

101:24

1 November

Most cationic vinylidene complexes (and “metal stabilized vinylcarbonium ions”*) react characteristically with alcohols or water to give alkoxycarbene or acyl (deprotonated hydroxycarbene) complexes, respectively.’.2 T h e reaction is thought to proceed by nucleophilic attack a t the vinylidene a carbon, followed by a proton shift from the (incipient) oxonium ion to the carbon. This is the behavior noted for [ ( C p ) F e ( C O ) z ( C = C H P h ) ] + (generated in situ) and [ (Cp)F e ( C O ) ( P P h , ) ( C = C H P h ) ] + under hydroxylic conditions.’

R

y

I

R’ R

I

M-C ‘OLH

-

MAC

-

/CHb-H* \OH

I

H

-75.9 88.5 78.0 87.2 -27. I 75.0

+

Equations of the Planes of the Form A X BY plane A B C 1

2 3 4

5 6

0.5571 -0.9001 -0.901 0 0.2095 0.9996 0:2354

0. I749 -0.2339 -0.2086 0.4475 0.005 I

-0.41 66

-0.8 1 18 -0.3676 -0.3804 -0.8694 -0.0290 -0.8781

base

-H+

+ CZ = D D 1.8047 -0.01 38 -1.2106 - 1.8968 - 1.9585 -0.2967

(‘ Atoms marked with an asterisk were not used in the calculation ol‘the plane.

with J p c = 37.4, J p t c = 16.8 Hz. O t h e r features of the I3C N M R spectrum of 111 a r e normal. Resonances d u e to the olefinic carbons (C(61) and C ( 6 2 ) ) were not found, presumably owing to long relaxation times and overlap with the intense phenyl multiplet.

/CHR, M-C \O

(5) However, the bis(phosphine) substituted vinylidene complexes [(Cp)Fe(dppe)(C=CRR’)]+ (la-c) and [(Cp)Fe(P(CH3)3)2(C=C(CH3)2)]+ ( I d ) a r e inert to alcohols and water.3.’2c A t higher p H , vinylidene complexes containing a P-hydrogen substituent are deprotonated to the corresponding iron alkynyl c ~ m p l e x . ’ , T~h~e, isobutenylidene ~ complex Ia,

Dihedral Angles between Planes planes angle, deg 1-2 2-4 2-6 3-4 3-5 5-6

21, 1979

Discussion

distance from plane

W 2 )

/

\I

-C

m

Adams, Davison, Selegue which does not contain a

Cationic Vinylidene Complexes

fi hydrogen,

reacts with hydroxide

or other bases by deprotonation of the coordinated dppe ligand, followed by cyclization of the zwitterionic intermediate IV.

7237 T o summarize, we have demonstrated that a coordinated phosphine in a cationic transition metal complex can show enhanced acidity a t t h e cy protons. T h e intermediate deprotonated phosphine complex can act as a carbon nucleophile toward another ligand in the coordination sphere of the metal. I n complex 111, the resulting ferradiphospha[2.1 .I]bicyclohexane ring system shows novel geometric and spectroscopic features reflecting torsional strain in the molecule.

Evidently, a coordinated phosphine in a cationic transition metal complex can demonstrate enhanced acidity of the cy protons. This effect is comparable to the greater acidity of a phosphonium salt relative to its parent phosphine ( e g , 4020b). pKa(Ph3PCH3+) x 1 5-2020a VS. pKa(Ph2PCH3) Complexes containing R 2 P C H R ' ligands, similar to intermed i a t e IV, have been isolated a n d c h a r a c t e r i z e d . Acknowledgment. W e thank t h e National Science Foun[P(CH~)~]~(H)[(CH~)~PCHZ]F~ appears to be formed by the dation for a graduate fellowship to J.P.S. and the Southern intramolecular insertion of electron-rich iron(0) into an adN e w England High Field N M R Facility (Biotechnology Rejacent P-C-H bond.21 Lithiated phosphines reacted with metal sources Program of the National Institutes of Health, G r a n t halides to form { [(Ph2P)zCH]NiBrJ222 and [P(CH3)3]3RR-798). [ ( C H ~ ) ~ P C H ~ ] C Formation O.~~ of three-membered P t - P - C rings in 1 - [ (P-H-(C,H~)~)P~(P-~-(C~H~)~CHC H 2CH3)] - 2-C6H 5 - 1,2- (a-B1oC2H 10)24a and related carboSupplementary Material Available: Structure factors and interrane c o m p l e ~ e was s ~ ~ascribed ~ ~ ~ to internal C - H metalation molecular contacts for 111 (1 3 pages). Ordering information is given on any current masthead page. promoted by the bulky carboranyl T h e coordinated carbonyl in [ ( C p ) F e ( d p p e ) ( C O ) ] + (V), which is isoelectronic with l a , is similarly unreactive toward References and Notes hydroxide, whereas [(Cp)Fe(PPh3)(CO)z]+ reacts with potassium hydroxide to form a stable hydroxycarbonyl complex (1) Davison, A,; Solar, J. P. J. Organomet. Chem. 1978, 755, C8-Cl2. ( C p ) Fe( PPh,)(CO)( C O O H ) .25 In fact, the ionic hydroxide (2) (a) Jolly, P. W.; Pettit, R. J. Organomet. Chem. 1968, 72, 491-495. (b) Chisholm, M. H.; Clark, H. Acc. Chem. Res. 1973, 6, 202-209. (c) Bell, salt [(Cp)Fe(dppe)(CO)] [ O H ] can be isolated.25 T h e low R. A.; Chisholm, M. H.; Couch, D. A.; Rankel, C. A. Inorg. Chem. 1977, 16, electrophilicity of the metal-bonded carbon atom in complexes 677-886. (d) Bell, R. A.; Chisholm, M. H. Inorg. Chem. 1977, 76, 687697. Ia-d and V relative to their carbonyl-containing congeners can (3) (a) Davison, A.; Selegue, J. P. J. Am. Chem. SOC.1978, 700, 7763-7765. be attributed to the better electron-donor capability of phos(b) ibid., in press. phine ligands, which in turn permits more effective metal to (4) Bruce, M. I.; Wallis, R . C. J. Organomet. Chem. 1978, 767, Cl-C4. (5) Mansuy, D.; Lange, M., Chottard, J. C. J. Am. Chem. SOC. 1976, 700, vinylidene (or carbonyl) T donation of electron density. T h e 32 13-32 14. lack of reactivity of trans-[Fe(depe)2CI(C=CHPh)]+ 8,26 (6) (a) Antonova, A. B.; Kolobova, N. E.; Petrovsky, P. V.; Lorshin, B. V.; Obezyuk, N. S. J. Organomet. Chem. 1977, 737, 55-67. (b) Kolobova, N. toward alcohols can also be rationalized in this way. T h e fact E.; Antonova, A. B.; Khitrova, 0. M.; Antipin, M. Yu; Struchkov, Yu. T. /bid. that the dppe ligand in V is not deprotonated by hydroxide is 1977, 137, 69-78. deserving of further study. (7) Andrianov, Y. G . ; Struchkov, Yu. T.; Kolobova. N. E.; Antonova, A. B.; Obezyuk, N. S. J. Organomet. Chem. 1976, 722, C33. T h e geometry of t h e polycyclic ring system of complex I11 (8)Abbreviations: Cp = g5-C5H5; dppe = 1,2-bis(diphenylphosphino)ethane; can be compared to two other systems containing M - C (sp2) L = neutral donor ligand; depe = 1,2-bis(diethylphosphino)ethane. linkages in constrained rings. In complex VI,27 t h e M n - C - P Mueller-Westerhoff, U. T.; (9) LeVanda, C.; Bechgaard, K.; Cowan, D. 0.; Eilbracht, P.; Candela, G. A.; Collins, R. L. J. Am. Chem. SOC.1976, 98, angle is reduced to 92.0' owing to t h e strain in t h e four3 178-3101. membered chelate ring. In t h e polycyclic complex V11,28t h e (IO) (a) Fischer, E. 0. Angew. Chem. 1957, 69,207. (b) Reynolds, L. T.; WilkC o - C ( I ) - C ( 2 ) angle is relatively unstrained a t 117.6', since inson, G. J. Inorg. Nucl. Chem. 1959, 9,86. (11) Wannagat, U.; Niederprum. H. Chem. Ber. 1961, 94,1540. it is involved only in six-membered chelate rings.

OWCHdz /,OCH(CHd, Nc